Antibody titre and avidity in saliva and serum are not impaired in mildly to moderately undernourished children.

Avidities and titres of serum IgA, IgM, IgG, and salivary IgA antibodies for poliovirus type 3, beta-lactoglobulin and E. coli O antigens were analysed in well-nourished (n=58) and mildly to moderately undernourished (n = 18) 1-7-year-old children, living in slums in São Paulo, Brazil, with irregular water supply and no sewage system. The serum titres of antibodies in the undernourished children were not statistically different from the well-nourished ones, except for the IgA anti-beta-lactoglobulin titres which were lower in the youngest undernourished group. In respect to avidity of the serum antibodies, no statistical difference was observed, except that the youngest undernourished children presented avidities of serum IgA anti-E. coli O antigens higher than those of the well-nourished children of the same age range. With respect to salivary titres and avidities no difference was observed between well-nourished and undernourished children. The fact that the undernourished children were not deficient in antibody amount or quality, as measured in this study, suggests that in this respect their immune system was not impaired.